North Korea will take steps to shut down its main nuclear reactor "within a day" of a freeze on its funds being lifted, a US delegation chief has said.
N Korea has pledged to shut down its main reactor
Bill Richardson said North officials had assured him they would invite back UN nuclear inspectors as soon as they had access to their money.
The funds, which have been frozen in a Macau bank, are expected to be released later Wednesday or Thursday, he added.
The issue has hindered efforts to meet Saturday's reactor shutdown deadline.
North Korea had asked for a further 30 days, beyond Saturday, to close its only operational reactor, Yongbyon, Mr Richardson said.
He had told the North Korean officials the US thought that was too long, he added.
"We let them know that this was not acceptable and the issue was dropped," Mr Richardson told a news conference in South Korea.
"Now the ball is in North Korea's court to take the next important steps."
Mr Richardson, New Mexico state governor and a US presidential candidate, was speaking after a four-day visit to the Communist state.
He was leading a delegation to retrieve the bodies of US soldiers killed during the Korean War.
He said officials in Pyongyang had assured him that once the funds were made accessible, the North would act swiftly to enact its pledge to shut down Yongbyon.
"The North Korean government told us that with that issue resolved, [it] would move promptly, within a day after receiving the funds," he said.
"And therefore, within that day, [it would] invite the [UN nuclear inspectors] to Pyongyang to draft the terms for shutting down the Yongbyon reactor," he added.
Mr Richardson said he was "optimistic" about the North's willingness to shut the reactor, which was part of a deal agreed in February.
Under that landmark agreement, North Korea said it would "shut down and seal" Yongbyon in return for energy aid and other incentives from its dialogue partners - the US, China, Russia, South Korea and Japan.
But the deal has been delayed because of the financial dispute involving $25m (£12.7m) of North Korean funds, which was frozen in Macau-based Banco Delta Asia (BDA).
The deadlock looked to have been resolved on Tuesday when the US Treasury Department said the Macau authorities would lift the freeze, allowing North Korea to obtain the money.
Senior US envoy to North Korea Christopher Hill said the issue should no longer block progress on the nuclear deal.
"I think we have come to a very important juncture which is that we consider this BDA matter to be really resolved," he said.
"The DPRK [North Korea] has access to their accounts now... We think it is a really important time to get on with the ever urgent task of denuclearisation, in particular to get on with the implementation of this February agreement."